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A181654
An eigentriangle of the number triangle A181653.
2
1, 1, 1, 2, 1, 1, 3, 2, 1, 1, 6, 4, 2, 1, 1, 9, 6, 3, 2, 1, 1, 18, 12, 6, 4, 2, 1, 1, 27, 18, 9, 6, 3, 2, 1, 1, 54, 36, 18, 12, 6, 4, 2, 1, 1, 81, 54, 27, 18, 9, 6, 3, 2, 1, 1, 162, 108, 54, 36, 18, 12, 6, 4, 2, 1, 1
OFFSET
0,4
COMMENTS
Generalized (conditional) Riordan array with k-th column generated by x^k*if(mod(k,2)=0,(1+x-x^2)/(1-3x^2),(1+x-x^2+x^3)/(1-3x^2)).
Row sums are A181655.
LINKS
Paul Barry, Invariant number triangles, eigentriangles and Somos-4 sequences, arXiv preprint arXiv:1107.5490 [math.CO], 2011.
EXAMPLE
Triangle begins
1,
1, 1,
2, 1, 1,
3, 2, 1, 1,
6, 4, 2, 1, 1,
9, 6, 3, 2, 1, 1,
18, 12, 6, 4, 2, 1, 1,
27, 18, 9, 6, 3, 2, 1, 1,
54, 36, 18, 12, 6, 4, 2, 1, 1,
81, 54, 27, 18, 9, 6, 3, 2, 1, 1,
162, 108, 54, 36, 18, 12, 6, 4, 2, 1, 1
CROSSREFS
Sequence in context: A049286 A308477 A079216 * A374757 A323756 A192710
KEYWORD
easy,nonn,tabl
AUTHOR
Paul Barry, Nov 03 2010
STATUS
approved